The present invention is directed to vibration damping control cryocoolers including free-piston engines. More particularly, the invention is directed to an active damping vibration controller for use with a cryocooler where low-vibration levels are required.
Sunpower® Inc. produces a product line of crycoolers under the trade name Cryo Tel®. The system vibration levels of the Cyro Tel® cryocoolers are greatly influenced by the mass, configuration, and rigidity of the system in which the cryocooler is installed. Sunpower® Inc. provides a passive (reactive) balance absorber that is tuned to mitigate a primary drive frequency of the cryocooler. With generic production tuning, the resultant free-body vibration acceleration of the system is approximately 300-400 milli-g (acceleration). This level of vibration is tolerable in many applications.
When lower levels of vibration are required, Sunpower® Inc. offers three options for further reducing vibration levels. First, in-situ tuning of the primary passive absorber when the cryocooler is mounted in the customer's system allows for addressing and mitigating the effects of the system design on the total system vibration. Second, a harmonic passive absorber or a dual-frequency absorber assembly that includes a first and second harmonic absorber may be installed on the cryocooler resulting in vibration levels of 200 milli-g and lower. Finally, an active (powered) absorber may be attached to the back of the cryocooler. The active damper can be driven by a closed loop driver that reads a vibration signal and provides a drive signal to the absorber to counteract the vibration energy. Vibration levels on the order of 40 milli-g can be achieved. Sunpower does not provided the drive system for the active damper.
Infrared (IR) and photo detectors potentially benefit from operation under cryogenic conditions. However, system vibrations can render the use of a cryogenic cooling system undesirable if the vibrations produce more noise for the detectors than the system inhibits. Other detector and sensor types benefit from the invention.
U.S. Pat. Nos. 7,458,143; 7,266,947; 7,043,835; 6,782,700; 6,684,637; 6,446,336; 6,293,184; 6,199,381; 5,642,088; 5,642,008; and 5,525,845 are assigned to Sunpower Inc. and directed to aspects of the Cryo Tel® line of cryocoolers. All the above listed documents are incorporated by reference herein in their entirety.